1. Field of the Invention
The invention relates to improved thickening systems for cosmetic compositions, particularly those in lotion and cream form.
2. The Related Art
Aqueous cosmetic compositions often require thickeners to achieve an aesthetically pleasing viscosity. Fluids that flow with a watery consistency too rapidly run off the treated skin areas. For a cosmetic to be effective, it often must have substantivity. Thickeners provide this substantivity. Furthermore, low viscosity formulas which may be skin effective nevertheless through their wateriness signal ineffectiveness to the consumer. Products of watery consistency are also aesthetically displeasing to consumers with expectations of rich and creamy products.
U.S. Pat. No. 5,422,112 (Williams) discloses a triple thickener system including xanthan gum, magnesium aluminum silicate and polyacrylamide. The compositions are said to be particularly effective for thickening alpha-hydroxy carboxylic acids and salts thereof, especially at low pH.
U.S. Pat. No. 5,874,095 (Deckner et al.) reports an enhanced skin penetration system for improved topical delivery of drugs. Essential to the system is a nonionic polyacrylamide of high molecular weight described as effective at low pH.
U.S. Pat. No. 5,952,395 (Lorant) and U.S. Pat. No. 5,891,452 (Sebillote-Arnaud et al.) describe cosmetic compositions gelled into an emulsion with a cross-linked poly(2-acrylamido-2-methylpropanesulfonic acid).
Countless numbers of other thickening agents are known in the literature. Perhaps this plethora intimates that not all thickening agents are equally effective for any particular type of formulation.
Indeed, there are some formulations which are extremely difficult to thicken, and even if initially thickened may have storage stability problems. Low pH systems are particularly sensitive and difficult.
Accordingly, it is an object of the present invention to provide a thickener system and thickened cosmetic compositions of sufficiently aesthetically pleasing viscosity and skinfeel.
It is another object of the present invention to provide thickening systems for cosmetic compositions that are effective at low pH.
It is still another object of the present invention to provide thickening systems for water and oil emulsion cosmetic compositions that also function as stabilizers preventing phase separation.
These and other objects of the present invention will more readily become apparent from the description and examples which follow.